diff --git a/server/prompts/overseer_control_system.txt b/server/prompts/overseer_control_system.txt
index 23fb7737..5c62b862 100644
--- a/server/prompts/overseer_control_system.txt
+++ b/server/prompts/overseer_control_system.txt
@@ -20,6 +20,7 @@ Actions:
 - Ask a question only if a required action parameter is missing.
 
 Chat output:
+- Always use English.
 - If speaking, send one short in-character live-chat line.
 - Keep it concise and informal (roughly 3-14 words).
 - Chat output must be spoken text only.